Room temperature preparation of highly stable cesium lead halide perovskite nanocrystals by ligand modification for white light-emitting diodes

The poor stability of halide perovskite nanocrystals (NCs) has severely hindered future practical application. Herein, we proposed a facile and effective ligand modification route to synthesize stable CsPbBr₃ nanocrystals by introducing a double-terminal ligand, namely 4,4′-Azobis(4-cyanovalericacid) (CA), to replace the conventional oleic acid (OA) ligand at room temperature. The as-synthesized CsPbBr₃-CA not only possesses high photoluminescence quantum yield (72%) related to the reduced trap defects, but also shows significantly improved stability exposure to water, ethanol, light, and/or heat benefiting from the CA ligand anchored to NC surfaces tightly. The photoluminescence intensity of CsPbBr₃-CA maintains about 80% and 75% of its initial emission intensity after immersed in water or ethanol for 360 min, respectively, whereas that of the CsPbBr₃-OA was quenched completely within a few minutes. Moreover, an all-inorganic white light-emitting diode (LED) covered 126% National Television System Committee (NTSC) standard and 92% Rec.2020 standard was fabricated by combining the green CsPbBr₃-CA and commercial red-emitting K₂SiF₆:Mn⁴⁺ (KSF) phosphors onto a blue LED chip. Thus, the presented work initiates the development of the room temperature preparation of high quality CsPbBr₃ and shows prospect for next-generation displays. [Figure not available: see fulltext.]